In a fluid apparatus or the like, it is important to achieve an efficiency improvement of the fluid apparatus and decreases in vibration and noise by controlling flow of fluid flowing inside the fluid apparatus.
As a flow control means, there has been developed a technique of plasmatizing part of fluid to generate a plasma induced flow. According to this airflow generation device, it is possible to generate a thin laminar flow on a flat plate, and to vary velocity distribution of a boundary layer of the flow. For this reason, by forcibly changing the flow from a laminar flow to a turbulent flow, and generating/eliminating a vortex flow, it is possible to control the flow of the fluid flowing inside the fluid apparatus and improve aerodynamic characteristics and the like of the fluid apparatus.
Further, the above-described airflow generation device is provided on two-dimensionally symmetrical blades, and pulse modulation control of intermittently increasing/decreasing or turning on/off a voltage to be applied to the airflow generation device is performed, and thereby efficient airflow control is made possible. Particularly, it is found that when a frequency of pulse modulation is set to a frequency in the vicinity of a dominant frequency of flow velocity variation detected in a blade wake flow, an effect of which a large-scale separation flow is drawn to the blade surface appears.
The above-described dominant frequency changes according to the size or structure of an apparatus, the relative velocity of fluid to an object, the viscosity of fluid, or the like. For this reason, it is difficult to estimate the dominant frequency except for the limited case such as a Karman vortex street of a cylinder wake flow. Thus, in the case of a dynamic flow of which a flow velocity or an inlet angle changes, installation of a fluid variation sensor for determining the frequency of the pulse modulation control is required, which causes an increase in manufacturing cost of the device.